Control for flash-welding machines



May 30, 1950 A. H; MCPHEE ET AL 2,509,606

CONTROL FOR FLASH WELDING MACHINES Filed Jan. 29, 1946 Patented May 30, 1950 CONTROL FOR FLASH-WELDING MACHINES Alexander H. McPhee, Brooklyn, and David Bruce Johnston, Mamaroneck, N. Y.

Application January 29, 1946, Serial No. 644,094

8 Claims.

This invention relates to a flash weldin machine and more particularly to a heavy duty flash welding machine and to means for controlling the operation thereof.

In such machines the welding operation comprises at least two stages. The preliminary burn-01f or preheating of the abutting surfaces which are to be welded and an upsetting operation during which the actual weld is formed. Where the weld has a large area the preheating or burn-01f stage must necessarily be fairly extended and the machine must be kept under extremely close control. Welding machines with which we are familiar have previously employed either of two means of controlling movement of the movable platen of the machine. Where the work is light and the machine small, the movement of the movable platen is controlled both in its preheating cycle and in the upset by a cam. Heavier machines as heretofore constructed have been controlled entirely by hydraulic apparatus either automatically or manually actuated through a follow-up valve. Cam operation is obviously limited to the smaller types of machines being entirely unsuited for use in machines where extreme pressures are necessary. Purely hydraulic operation is objectionable in that a small amount of wear in the follow-up valve or lag therein or a very small amount of air in the hydraulic system will result in an erratic motion of the moving platen with the resultant sticking or short-circuiting of the welding current through the members being welded prior to the obtainment of a suflicient degree of heat for proper welding.

An important object of the present invention is the provision of a control for heavy duty flash welding machines of such nature that the movement of the movable platen during the burnoff" is under absolute control and in which, at the same time provision is made for a rapid and high pressure closing of the movable platen during the welding or upset.

Another object of the invention is to provide a control of this character including what may be termed a preliminary burn-01f efiective prior to the actual "burn-01f period and acting to compensate for inequalities of inaccurate lengths of the members to be welded which might tend to cause sticking during the early stages of the "burn-01f and which will eliminate the necessity for extreme accuracy in surfacing of the faces to be welded. This operation is known as sizing burn-off.

Another object of the invention is the provision in a control of this character of an arrangement whereby, in the event of sticking, the controls may be actuated to efiect a rapid opening of the platens and separation of the members being welded. These and other objects we attain by the control shown in the accompanying drawings in which- Fig. 1 is a diagrammatic view of layout of a welding machine control constructed in accordance with our invention; and

Fig. 2 illustrates a typical form of cam for use in the machine.

Referring now more particularly to the drawings, numerals II and I0 designate respectively the movable and fixed platens of a heavy duty flash welding machine. The movable platen has connected thereto a ram IL in pressure cylinder l3 and connected to this ram and moving therewith as through yoke I4 are the pistons I 5 of auxiliary cylinders l6. These cylinders supply the pressure through a liquid system including a pump l1 withdrawing liquid from a sump l8 and discharging either directly to the closing ends of cylinder l6 or to an accumulator [9, including air pressure tank 20. Through control mechanism, hereinafter more fully described, the pressure of accumulator l9 may be imparted simultaneously to the closing ends of cylinders l6 and to the cylinder l3 or to the opening ends of cylinders I6. Yoke I4 is connected to the ram of cylinder [3 by rod 2|, this rod bearing an adjustable nut 22 by which means the permissible movement of ram l2 may be adjusted and being provided at its end with a contact roller 23.

Contact roller 23 is adapted for cooaction with a cam 24 which cam is mounted upon a carriage 25 guided by tracks 28 and shiftable upon these tracks from an operative position in which the cam may engage the movable platen [0 through roller 23, rod 2| and ram 12, to an inoperative position suggested by the dotted lines of Fig. 1 in which it is so withdrawn from roller 23 that it may not engage therewith without regard to its position. As at present shown, an air pressure cylinder 21 through a rack 28 operated from the piston thereon rotates gears 29 through which arms 30 are oscillated, these arms being linked to the carriage 25 as at 3| and serving to move the carriage in the direction of the arrow A Fig. 1 at the emergency withdrawal of cam 24 or to shift the same in the opposite direction to restore the carriage to its normal, fully illustrated position. This cylinder as more fully described hereinafter is actuated from pressure tank 20.

Operation of the elements just described is controlled as follows: Assuming the press to be in position illustrated diagrammatically in Fig. 1, pump I1 is in operation and accumulator I9 is charged. Valve 42 is open and permits the entire discharge of pump I! to return directly to sump [8. The press is fully open and there is no pressure present in the hydraulic controls thereof. The cam is in the returned position. The controlspf the press are-preferablyelectrical-and have been general-ly indicated by various electrically operated valves and limit switches hereinafter more particularly referred to.

In starting the press, and perform-ing what-may be called closing thereof, during which the press is shifted from its full openposition to a posi-' P tion where the ends of the work are-brought into position for welding, valve 142 is shifted? making pressure available to valve 32 and valve 32 normally blocked at all ports is positioned to admit fluid pressure from ther-pump to the closing ends dflfuicyljindels L6; The press :moves (forward on closing: stroke" untilwlimit, switch; :38 returns waive 32 to: normal position. During this time who/cylinder 1:3 is-iill'ed by gravity; from sump E8 athnoughiill-ing-cheok valve 48; :During this movel mentsaiylimit switch "34; controlling operationof motor 35, operating screw 36 by means .of which .-;ithe cam 24'i is actuated is 4 returnedto normal Hpositioni and=.=a secondlimit: switch 3 1 is; actuated, energizing motor 3*5:.and",advancing cam- 24 1 at rim-11', speed- During {this timethe movement of movable platen It continues and acfurtherlimit rswitch -38 is actuated? fIhisswitchservesto're- '-;tl1 n-val=ves Bland-:42 to their normalpositions in :.w fctn as-heretofore;descr%ilced, the pump'pressure 1$:dlV81'WdfiQ-il7h6, sump;- l8 thus-stopping the press. Gonfinued forward movement of camT-ZQ- brings it intmcontact with the roller2-3 andthe engagement of: the: cam :and roller through an incline on the, cam--advances the platen: ii] to; a short distance, as for example onequarterinch and causes: thepam --to actuate a --l imitswitch C 4] Leheckingroperation-thereof.

:The machine is now positioned for, the welding :opera-tioh and" when this isinitiated, forward :movementof cam Zipontinues, the cam-moving ionward! at; adiusted speed; and closingthe press.

moreiolearly" shown in :Eig; 2 thecam, adja- ;cent--=to incline; =39,.preferably includes a very gslight; slope ff lii causi-ng: a slow-forward operation followingthe; application of-ywelding ourrent and permitting the {sizing burn off. hereinbeforere- ;ferred ;to,.,f,ollowing which the am feeds the platen v (-9 forward at an, adjusted speed deter,-

,-1ii.ined particular1y; for the workatha-nd- (varia- I z ti onslin operationiwill require; variedcam; struc- ::tw'5es) to complete the burn-oft operation. rllliming g'thistburn-oil operation, if--it be so dersjred,.-,.the intensity; of welding voltage may he -ohanged=as the platen Illadvance'sto regulate the v uloseaandithereby preventing the escape of presasiirefrom cylinder- 13; :Valve32-admits1pressure toclosingsideot cylinders l 6.-

Aspreviouslynoted; it; sometimes occurs ,dGSPitB close calculations 3811111 careful preparation; that rfst ek nslii ccurs d r net rn-0 t -=d camto its inoperative position, it being recalled that the cam, during this period, will be in alinement with the roller and arranged in the effective path of movement of this roller during any rate of open movement of platen It. As the carriage 2:5 approaches its withdrawn position at which the earn 2'4, -'-regardless of its position, will be clearof movement with roller 28 in its extreme left hand position, (Fig. 1) a limit switch or other control indicated at 44 actuates valve 32 to connect the left hand ends-of cylinders It with sump t8;-,and' at thesame time actuates a-valve: 45; by "means of. which accumulator pressure is admitted -to the-r-ight hand ends of cylinder 16 thereby opening the press. I

In additionto the above, provision isma'defor -.-r.et urning the cam automatically after the normal upset stroke and'ior returning the movable platen .to tlieflopen' positionso that the cycle may/be emak :Also, all movements of the press and cam. may

be operated individually and separately so-=that adjustments, can bev made. During-- all operations .interlocksare provided for preventing the interference, of, parts which occupy the semespaeeat 1differ'enttimes during the normal welding c cl It .w'illabe obviousfrom the rore oin mmjpy use of a pressicontrol constructed iii-accordance ,witl our invention the usutl safety factors' im'ay maintaihed'while at the same tinie enabling ,tive andaccurate controllo'f both the blu'rhe anaupsettmg cycles of theweld-forrningf ope :ti'on. It willlalso be obviousthat the present-fil lustration is, purely-diagrammatic and capableof considerable variation in actual practice. We do not,.. accordin'gly, wish to be understood as limiting ourselve to. the arrangement shown except as hereinafter.ekplained.

-We cla m: 7 r .1. aflash welding machine, a pressha i n g fixed r and 'movable platens, mechanicalwcam -means-to closathe platens during the fbu-rn-Qill period of a welding operation, and hydraulic means effective: after a predetermined closing movementoftheplatens by the cam to. effect an upset at the were;

,2. Ina fiashweldingmachine, .a press-having fixeid and movable' platens, mechanical -;ca m me'anstfo closethelatens duringthe burneoff periodYof a welding operation, .and' hydraulic means effective after a ,predetermind' closing movementoflthe platens by the cam to. effectiagn upsetatkthe weld, said'cam means having twp positions in one of which-it: may be engagedfwith ithe movable platento movethe same and'ih the other, of which it isrunengageable therewith; -and means for moving said cam to the lastnamed posit'ionand thereafter actuating saidrhyd rau lic means ,to' open. said platens;

3. Ina flashrweldingmachine, a pressv having fixed and movable platens adapted to receive membersto be weld oonnected, hydraulic means Ito-shift said platens to bringrsaid members into engagement mechanicalcam means to eiT-ectengagement of' the members during the-burn-off lu period of the welding operation, and ,means to acoaeoe actuate said hydraulic means effective only after a predetermined closing movement of the platens by the cam means for upsetting the members at the weld.

4. In a flash welding machine, a press having fixed and movable platens adapted to receive members to be weld-connected, hydraulic means to shift said platens to bring said members into engagement, mechanical cam means to effect engagement of the members during a burn-off period of the welding operation, and means to actuate said hydraulic means effective only after a, predetermined closing movement of the platens by the first named means for upsetting the members at the weld, said cam means having two positions in one of which it may be engaged with the movable platen to move the same and in the other of which it is unengageable therewith, and means for moving said cam to the last named position and thereafter actuating said hydraulic means to open said platens.

5. In a flash welding machine, a press including fixed and movable platens having open and closed positions, means to close the platens, cam means to further close the platens during "burnofi of elements to be welded mounted thereon, means to apply pressure to upset said elements, and means operable at will during said burn-off for opening said press.

6. In a flash welding machine, a, press including fixed and movable platens having open and closed positions, means to close the platens, cam means to further close the platens during burnoil of elements to be welded mounted thereon,

hydraulic means to apply pressure to upset said elements, means operable at will during said "burn-off for opening said press, said cam means having two positions in one of which it may be engaged with the movable platen to move the same and in the other of which it is unengageable therewith, and means for moving said cam to the last named position and thereafter actuating said hydraulic means to open said platens.

7. In a flash welding machine, a press having fixed and movable platens, means including a motor-driven cam for actuating the movable platen during the burn-off period of a, welding operation, and hydraulic means rendered operative at the completion of said period for actuating the movable platen rapidly and under high pressure to effect an upset at the weld.

8. In a flash welding machine, a press having fixed and movable platens, a pressure cylinder, a ram in said cylinder connected to the movable platen, a rod extending from said ram to the exterior of said cylinder, hydraulic means for actuating said rod to close said press, mechanical cam means for actuating said rod so as to move the movable platen during the burn-off period of a welding operation, and means for actuating said ram hydraulically to effect an upset at the weld.

ALEXANDER H. McPHEE. DAVID BRUCE JOHNSTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,957,759 Coates May 8, 1934 2,015,914 Weightman Oct. 1, 1935 2,085,049 Spire June 29, 1937 2,409,850 Hackett et a1. Oct. 22, 1946 

